Nowadays, the connection between the piston rod and the piston of a hydraulic cylinder usually is tightened with a specified angle of rotation. However, the specified angles of the threaded connection, in particular with piston sizes having a piston diameter of 200 mm and more, only can be achieved with very high tightening torques.
Nowadays, the connections between piston rod and piston therefore usually are tightened and released with great stationary tightening machines, wherein the piston rod is clamped on the side facing away from the piston and the piston is tightened by the tightening machine. Furthermore, screw-on wrenches are known, which are moved with a sledgehammer. The connections often are hardly tightened or only insufficiently, since the necessary torque cannot be applied.
On the whole, no satisfactory solution is known so far, by means of which the screw connection between piston and piston rod can be achieved with the necessary tightening torques, in particular in harsh usage on the construction site.
Therefore, it is the object of the present invention to provide a tool for screwing a piston onto the piston rod of a hydraulic cylinder, by means of which the necessary tightening torques can be applied with easy manageability at the same time. Furthermore, it is the object of the present invention to provide a hydraulic cylinder, for which the tool of the invention can be used.
This object is solved, in one example, by a tool for screwing a piston onto the piston rod of a hydraulic cylinder, in particular of a hydraulic cylinder with a piston diameter of more than 200 mm, including a first tool element with connecting elements for releasable connection with the piston and a second tool element with connecting elements for releasable connection with the piston rod, which is rotatable with respect to the first tool element. By rotating the first tool element against the second tool element, the torque necessary for screwing together piston and piston rod can be applied onto the piston and the piston rod via the connecting elements. Advantageously, the first tool element is rotatably mounted on the second tool element. Mounting the first tool element on the second tool element can be effected either directly or via one or more intermediate elements. The bearing allows a rotary movement between the first and the second tool element about an axis of rotation which corresponds to the axis of rotation of the screw connection between piston and piston rod, when the tool is connected with piston and piston rod.
In accordance with the invention, a tool is provided, by means of which the piston can be screwed onto the piston rod of the hydraulic cylinder safely and comfortably, wherein the necessary tightening torques can be applied in a controlled way. There is provided a mobile tool, which represents an economic alternative to existing stationary tightening machines. In particular, the tool can easily and comfortably be used on the construction site. The connecting elements of the tool engage the piston rod on the piston side, in particular they engage mating connectors arranged on the piston side. In particular, the advantage is obtained that the piston rod no longer must be fixed on the side facing away from the piston, since the second tool element engages the piston rod on the piston side. In this way, a compact tool can be provided, which can easily be transported and handled by a single operator.
Advantageously, the connecting elements engage the end faces of piston and/or piston rod. In this way, the tool can be designed extremely compact. The piston usually includes a through-bore, into which the piston rod is screwed, so that the piston-side end face of the piston rod is accessible. On this piston-side end face of the piston rod, mating connectors advantageously are provided, which are engaged by the connecting elements of the tool.
Advantageously, the connection of the connecting elements with piston and/or piston rod is effected by positive connection. In this way, a safe connection is obtained, by which high tightening torques can be transmitted.
Advantageously, the connecting elements comprise studs which can be inserted into recesses in the piston and/or piston rod, wherein inserting advantageously is effected axially. In this way, the tool can easily be connected with the piston and/or piston rod, in that it is advantageously pushed onto the piston and/or piston rod in axial direction. Advantageously, the tool can be pushed onto the piston and the piston rod at the same time, so that the connection between the tool and the piston and piston rod is effected in a single step.
Advantageously, the tool of the invention furthermore includes a power device, in particular a transmission, especially a spindle transmission, by means of which the rotary movement between the first tool element and the second tool element can be produced. The power device thus generates the high torques necessary for tightening piston and piston rod, which are applied onto piston and piston rod via the first and second tool elements.
Advantageously, the power device includes a connecting element, via which it can be driven by means of any kind of external drive, in particular an electric screwdriver. The power device, in particular in the form of a transmission, especially in the form of a spindle transmission, thus can easily be driven via an external drive, so that the tool itself can do without a drive. In this way, the tool can again be configured compact and at low cost, wherein the drive is effected by drives anyway present on construction sites, such as by an electric screwdriver. For moving the lever arms, any kind of power devices can be used. For instance, a hydraulic cylinder driven with a small compact unit can be employed advantageously. What might also be used for instance are electrohydraulic cylinders or pneumatic cylinders or any other linear drive.
Advantageously, the first tool element and the second tool element include lever arms, via which the torque is introduced into the first tool element and the second tool elements. In this way, a high torque can be produced by the leverage of the lever arms.
Advantageously, a power device, in particular a spindle transmission, is provided between the lever arms of the first and second tool elements, via which the torque is produced. In this way, a compact arrangement is obtained, by means of which high tightening torques can be produced in a controlled way. In particular, the use of a spindle transmission provides for controlled tightening with high tightening torques, without a particularly powerful drive being necessary for this purpose.
Furthermore advantageously, the tool of the invention includes one or more adapters, by means of which the tool can be used for different pistons and/or piston rods. The adapter advantageously is connected with the connecting elements of the tool and itself includes connecting elements, by means of which the adapter can releasably be connected with the piston and the piston rod of the hydraulic cylinder. The adapter transmits the torques necessary for tightening piston and piston rod also to those hydraulic cylinders which have mating connectors which are not compatible with the connecting elements provided on the tool.
The present invention furthermore comprises a hydraulic cylinder with a piston rod and a piston screwed onto the piston rod, in particular a hydraulic cylinder with a piston diameter of more than 200 mm, wherein piston and piston rod include mating connectors for releasable connection with the connecting elements of a tool for screwing the piston, in particular mating connectors for releasable connection with the connecting elements of a tool as shown above. In such a hydraulic cylinder, the tool of the invention accordingly can be used for easily and reliably tightening the piston on the piston cylinder.
The present invention furthermore comprises a piston rod for a hydraulic cylinder as shown above with piston-side mating connectors for releasable connection with the connecting elements of a tool for screwing the piston. Furthermore the device comprises a piston for a hydraulic cylinder as described above with mating connectors for releasable connection with the connecting elements of a tool for screwing the piston. By means of the piston-side mating connectors on the piston rod and the mating connectors on the piston, the mobile tool of the invention can safely and easily be used in accordance with the invention for mounting a new piston on a piston rod for instance on a construction site.
In the hydraulic cylinder, the piston rod or the piston, the connection between the connecting elements and the mating connectors advantageously is effected by positive connection. Connections via which the necessary high torques can be transmitted thus can be produced with simple constructive means.
Advantageously, the mating connectors are arranged on the end faces of the piston rod and/or piston. In this way, a relatively small-size tool can be used, which merely must engage the end faces of piston rod and piston.
Furthermore advantageously, the mating connectors comprise recesses in which the connecting elements of the tool can positively be inserted, wherein inserting advantageously is effected axially. In this way, the releasable connections between tool and piston and piston rod can be produced quickly and yet safely.
The present invention furthermore comprises an adapter for a tool as shown above, by means of which the tool can be used for different pistons and/or piston rods. The adapter thus allows mounting different hydraulic cylinders with only one tool, in that the adapter provides the connecting elements necessary for the mating connectors on the respective piston or on the respective piston rod.
The adapter includes first and second adapter elements, which are rotatable against each other. Advantageously, the two adapter elements rotatably rest against each other. The adapter includes mating connectors for connection with the connecting elements of the tool and connecting elements for connection with the mating connectors of the piston and the piston rod. The first adapter element carries the mating connectors for connection with the connecting elements of the first tool element and the connecting elements for connection with the mating connectors of the piston, whereas the second adapter element carries the mating connectors for connection with the connecting elements of the second tool element and the connecting elements for connection with the mating connectors of the piston. The mating connectors of the adapter can constitute recesses in which engage the connecting elements of the tool. The connecting elements of the adapter can constitute studs which engage in the mating connectors constituting a recess in the piston and piston rod.
There can be provided a plurality of adapters which allow to employ the tool of the invention with a plurality of different hydraulic cylinders.
Furthermore, the present invention comprises a working machine, in particular a traveling working machine, in particular a construction machine, in particular a hydraulic excavator, with at least one hydraulic cylinder in accordance with the invention.